import React from 'react'
class Clock extends React.Component {
  constructor (props) {
    super(props)
    this.state = {date: new Date()}
  }

  componentDidMount() {
    this.timerID  = setInterval(() => {
      this.setState({
        date: new Date()
      })
    }, 1000)
  }

  componentWillUnmount () {
    clearInterval(this.timerID)
  }

  render () {
    return (
      <div>
        <h2>It is {this.state.date.toLocaleTimeString()}.</h2>
      </div>
    )
  }
}

export default Clock